why are special lines useful in classifying stars?

a. they indicate a star's age..
b. they show the composition of a star.
c. they show the layers that make up a star.
d. they show a star's location.

1 answer

Special lines, also known as spectral lines, are useful in classifying stars primarily because:

b. they show the composition of a star.

Spectral lines are unique signatures of the elements present in a star's atmosphere. By analyzing these lines, astronomers can determine which elements are present, their abundances, and other properties related to the star's composition. This information is crucial for classifying stars and understanding their physical characteristics and evolutionary states.